Strengthening of duplex Mg–9Li–3Al–2Zn–1Sn alloy by solid solution and mixed rolling-induced second phase transition

Abstract

This work investigated the microstructure and mechanical properties of Mg–9Li–3Al–2Zn–1Sn alloy after solid solution and mixed rolling (hot rolling followed by room-temperature rolling). The research results reveal that after solid solution, AlLi and Mg2LiZn3 phases disappear, while MgLi2Al phases partially disappear. The hardness of the β-Li phase is much higher than that α-Mg phase, and the strength of the alloy is significantly increased while the elongation decreases to 1.4 %. Low plasticity is mainly due to lattice distortion and the presence of coarse Sn-rich phases. After mixed rolling, a large quantity of second phase precipitation in the alloy plays a role of second phase strengthening. The Mg17Al12 phases are observed to precipitate inside the α-Mg phase, and the AlLi phases containing MgLi2Al and Mg2LiZn3 nanophases inside are found at the β-Li phase and α-Mg/β-Li phase interface. The YS and UTS of the mixed rolled alloy reach 253 MPa and 273 MPa, respectively, with an improved EL of 18.4 %.